The present invention relates in general to an inverter apparatus which is capable of running an AC electric motor at an adjustable speed, and further readily modification of the specification and performance thereof.
An inverter apparatus which is capable of running an induction motor at an adjustable speed is utilized in various kinds of applications, and various kinds of inverter apparatus having various performances and functions are utilized depending on the applications. Now, a conventional inverter apparatus will be described by taking a general purpose inverter apparatus as an example.
This general purpose inverter apparatus has a configuration as shown in FIG. 11. An induction motor 5 is driven by an AC power source 4 through a main circuit unit 100. The main circuit unit 100 includes: a converter 101 (while in actual, it is configured by three-phase bridge connection of diodes, it is schematically depicted in the figure for the sake of simplicity); a smoothing capacitor 102; an inverter 103 as a DC/AC converter (while in actual, it is configured by three-phase bridge connection of switching diodes (power transistors or the like), it is schematically depicted in the figure for the sake of simplicity); a thermistor 104; a resistor 105 for detecting a current; and the like. In addition, a power source sensor unit 110 includes: a power source circuit 111 for producing various kinds of DC voltages; detection units such as a current detection unit 112 for detecting a current of the main circuit unit, a voltage detection unit 114 for detecting a voltage thereof, and a temperature detection unit 115 for detecting a temperature thereof; a drive circuit 113 for supplying a drive signal to the inverter 103; and the like.
A control.cndot.input/output unit 120 includes: a microcomputer 121 as a main portion; a storage device 122; an operator 126, and an input circuit 124 and output circuit 125 having respective connection terminals which elements constitute an input/output interface; and the like. A user operates the inverter apparatus using the operator 126, and connects wires to the signal connection terminals of the input circuit 124 and the output circuit 125, respectively, thereby controlling the inverter apparatus from the external controller.
The above-mentioned microcomputer 121 manages the running of the inverter 103 in accordance with the signals outputted from the input circuit 124 and the operator 126 under the program control thereof. For example, this management by the microcomputer 121 relates to the determination of the frequency and the voltage, the production of the drive signal, and the like, and in addition thereto, the selection of the running method is included therein. Further, the microcomputer 121 carries out the protection operation in accordance with the signals outputted from the various kinds of detection circuits. On the other hand, in the case where the frequency, the rotational direction or the current is determined and also the protection operation is carried out, the data relating to the protection factors thereof and the like is outputted to the operator 126 to be displayed thereon.
In this connection, there is an inverter apparatus which is of a type in which the above-mentioned operator 126 is mounted on the associated substrate or only the operator 126 is separated from other units so as to be able to be installed in the different position.
On the other hand, as an example of the inverter apparatus which is devided into two blocks, there is known one disclosed in JP-A-2-211039. This type of inverter apparatus is such that the servo motor is an object, i.e., the power devices, and the base driver and the current detection unit as the peripheral circuits thereof are incorporated in the form of one pack of module in the motor body, and the control unit is provided on the controller side, and also the interface between the motor side and the controller side are carried out by utilizing the optical communication.
As described above, in the conventional general purpose inverter apparatus, the microcomputer 121 carries out both the management of the input/output interface and the management of the main circuit unit 100 on the inverter 103 side. In this connection, the management of the main circuit unit is inherent in the converter apparatus and hence does not depend on the functions required by a customer. On the other hand, the contents of the management of the input/output interface vary depending on the requests issued from a customer. For this reason, if the standard functions and performance which are prepared on the maker side do not fulfill the requests issued from a certain customer, then the software of the microcomputer 121 needs to be changed and the change of the operator 126, the input circuit 124 and the output circuit 125 will also be necessary as the case may be.
As a result, there arises a problem that the software of the microcomputer and the hardware of the input/output interface needs to be reproduced depending on the contents of the customer's requests. When changing the software of the microcomputer 121, if the program is stored in the internal memory (ROM) of the microcomputer 121, in particular, the exchange of the microcomputer 121 itself needs to be carried out.
In addition, the input circuit 124 and the output circuit 125 are conventionally fixedly mounted to the inverter apparatus and hence can not be separated from other constituent elements. For this reason, the main circuit unit 100, and the input circuit 124 and the output circuit 125 must be installed in the same place.
On the other hand, in the above-mentioned example of the separative construction of the servo motor, the technique of separating the control unit, i.e., the inside of the controller into the power unit and the peripheral circuits thereof is merely disclosed. More specifically, while the control unit side thereof is made a new controller, including the optical interface with the power unit and the peripheral circuits thereof, the above-mentioned example does not refer to the input/output of the data between the external device and the controller at all. JP-A-2-65674 and JP-A-1-291693 show an inverter apparatus not capable of modification of the specification and performance thereof.